Question

Purification of chromium can be achieved by electrorefining chromium from an impure chromium anode onto a pure chromium cathode in an electrolytic cell. How many hours will it take to plate 12.5 kg of chromium onto the cathode if the current passed through the cell is held constant at 35.5 A

Answer 1

Answer:

544.522 Hours

Explanation:

a) Mass = 12.5 kg = 12500 g

Now, Number of moles is given as

No of moles = Mass of Cr / Molar mass of Cr

$=\frac{12500}{52}$

= 240.38 moles

$Cr^{3+}\Rightarrow$ 3 mols of electrons are required

$\Rightarrow 240.38\times3 =721.14\text{mol of e-}$

Converting moles of e- to coulombs of charge, (1 mol of electrons = 96500 C )

Q =721.14 mol×96500 C/mol

=69590010 of charge

We know that, Q = I×t

where Q is charge, I is current and t is time required.

$\Rightarrow t =\frac{Q}{I}$

$=\frac{69590010}{35.5}$

=196281.97 seconds

$=\frac{1.96281\times10^5}{3600}$

=544.522 Hours